According to JP-A-2000-42309, an element replaceable type fluid filter is disclosed. A drain member (drain plug 15) is screwed into a drain hole formed in a cap (lower case 12). The drain member 15 is loosened and removed from the drain hole so that the drain hole is opened and remaining oil is drained before an upper case 11 and the lower case 12 are detached from each other for replacing a filter element 13. Thus, oil remaining in the housing can be drained from the drain hole.
When the filter element 13 is replaced, an engine may be warmed up and oil may be heated in the fluid filter. In this situation, remaining oil is drained simultaneously with unblocking the seal member (packing) 15a of the drain member 15. As a result, heated remaining oil may flow out of the drain hole, and the oil may drip to hands of a worker when the drain member 15 is removed. Besides, the oil may splash in an engine room, and the engine room needs to be cleaned.
According to JP-A-11-104408, a cylindrical drainpipe member (drain plug 15) having a drain passage (central hole 15g, window hole 15f) is screwed into the drain hole formed in a cap (lower case 12) in a replaceable type fluid filter.
When the fluid filter is used for filtering fluid, the drain passage of the drainpipe member and the inside of the housing are blocked with each other by a pair of a seal member (packing 15g) provided on the outer circumferential periphery of the drainpipe member. When the filter element 13 is replaced, the drainpipe member is loosened, so that the upper seal member is unblocked, and the drain passage and the inside of the housing are communicated with each other. Oil remaining in the housing is drained through the drain passage of the drainpipe member, so that drained oil can be restricted from dripping to hands of a worker.
When the drainpipe member is loosened and the upper seal member is unblocked, blockade of the lower seal member is maintained, so that remaining oil does not leak from a portion excluding the drain passage of the drainpipe member when remaining oil is drained.
However, in this fluid filter, the drainpipe member is hollow to internally form the drain passage. Therefore, dust may intrude into the inside of the housing from the outside through the drain passage of the hollow drainpipe member when the fluid filter is used for filtering fluid. Accordingly, it is difficult to maintain blockade of the seal member of the drain hole.